PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Size 7 Earthies Teal/turquoise colour Mint Bindi Style , Women's No Brand Ballet Flats Soft Hot Pink Size 9 1/2 Casual Shoes NEW , Cole Haan Women’s Sling Back Flats 7.5 AA burgundy khaki canvas ballet flat shoeWomen's Classic Perforated Moccasin Loafer Flats Casual Shoes (VIVI-02) , Ladies Spot On Shoes Label F8813 , Talbots Womens Loafers Flat Shoes Soft Leather Upper Navy Blue 8 BBass Dune wheat enfield oxford hand painted black flash & charms nib sz 8MRemote Control Rubber Sole Multi Color Floral Leather Loafers/Driving Shoes 5.5 , Natural Soul by Naturalizer 'Francis' Shoes Women's 6M Brown Suede Slip On Mocs , Womens Skechers On The Go 600 Walking Cushioned Lightweight Flip Flops US 6-11SAS "Comfort Moccasin" leather oxford shoes USA women's sz 8.5 M ~ PERFECT SHAPEBreckelle's Women's 'Alice-22' Bow-detail Round Toe FlatsTroy Burch Women's Verbena Tribal Smoke Roccia/Black Ballet Flat , CLOGS BY KLOGS CONNIE TAUPE SUEDE TAPESTRY LEATHER WOMEN'S SHOES 8 MDavid Tate Luscious Slip On Shoe - Women's Size 12WW Silver , BOBS from Skechers Womens Bobs World-Daisy and Dot Flat- Pick SZ/Color. , Women's GEOLITE Leather Hiking/ Trail Shoes (Size: 7.5M) , Adidas Womens Running Shoes Size 9 (3143) , Teva Womens DE LA Vina Dos Chelsea Leather Waterproof Ankle Boots Size 10Rocket Dog Magic Canvas Pastel Foxing Casual Women's Shoes Size , Women's PUMA Baskets P.38 (UK.5) Blanches Genuine Athletic Shoes , REEBOK EASYTONE TONING TRAINING WALKING SNEAKERS WHITE REENEW WOMENS SIZES 10-12 , Customized Dog Print Running Shoes For Women-Free Shipping-Designed By Anne-Gret , New Balance Womens Wl696kc Brown Running Shoes Size 9.5 (18035) , New Balance 993 Women's Black Gray White Shoes Size 12 12D WideWomens Stretchy Pull on Casual Athletics Fashion Sneakers Hot Comfort Trainers , MERRELL MOAB VENTILATOR WOMENS HIKING TRAIL SIZE 9.5 ALUMINUM MARLIN J57758SAUCONY Women's Grid Cohesion 3 -White/Silver/Pink- Running Shoe , Converse All Star Chuck Taylor OX 147140F Periwindle Women Shoes *NO BOX , Vans Women's Atwood Low Rock Textile Gray Skate Shoes-Size 7.5/8.5/9/9.5/11 NWOB ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."